Menstrual Cycle | Medical Science Optional Notes for UPSC PDF Download

Changes During Menstrual Cycle

• LH Surge and Ovulation: Ovulation is triggered by an LH surge. Following ovulation, as the oocyte enters the fallopian tube, the ruptured follicle undergoes transformation into the corpus luteum, responsible for progesterone production. If no pregnancy occurs, the corpus luteum regresses, leading to a drop in progesterone levels.
• Uterine Cycle: At the conclusion of menstruation, all layers of the endometrium except the deep layers are shed. A new endometrium begins to regenerate under the influence of estrogens from the developing follicle. From the 5th to the 14th days of the menstrual cycle, the endometrium rapidly thickens. During this proliferative or follicular phase, the uterine glands lengthen without significant convolution or secretion.
• Post-Ovulation Changes: Following ovulation, the endometrium experiences increased vascularity and mild edema due to the influence of estrogen and progesterone from the corpus luteum. The glands become coiled and tortuous, initiating the secretion of a clear fluid. This phase, characterized by secretory or luteal changes, marks this later part of the cycle.

Vaginal Cycle

In response to estrogens, the vaginal epithelium undergoes cornification, with identifiable cornified epithelial cells in the vaginal smear. When influenced by progesterone, thick mucus is secreted, and the epithelium undergoes proliferation, accompanied by leukocyte infiltration.

Cyclical Changes in the Breasts

Despite lactation typically commencing at the end of pregnancy, cyclical changes occur in the breasts during the menstrual cycle. Estrogens induce the proliferation of mammary ducts, while progesterone promotes the growth of lobules and alveoli.

Common Disorders of the Menstrual Cycle

• Amenorrhea: Absence of menstruation, considered a symptom rather than a distinct disease.
• Oligomenorrhea: Characterized by infrequent, irregularly timed episodes of bleeding, typically occurring at intervals exceeding 35 days.
• Polymenorrhea: Involves frequent episodes of menstruation, usually happening at intervals of 21 days or less.
• Menorrhagia: Denotes regularly timed episodes of bleeding with excessive volume (more than 80 mL) and/or prolonged flow (over 5 days).
• Metrorrhagia: Refers to irregularly timed episodes of bleeding superimposed on normal cyclical bleeding.
• Menometrorrhagia: Involves excessive and prolonged bleeding occurring at irregular intervals.
• Hypomenorrhea: Describes regularly timed but scanty episodes of bleeding.
• Intermenstrual bleeding: Refers to bleeding (typically not excessive) occurring between otherwise normal menstrual cycles.
• Precocious Menstruation: Occurrence of menstruation before the age of 10 years.
• Postcoital Bleeding: Signifies vaginal bleeding after sexual intercourse.

Reproductive physiology-Repeats

Menstrual Cycle:

• Define the menstrual cycle and elucidate the alterations occurring in the uterus throughout this cycle. Identify the common disorders associated with the menstrual cycle. (2009)
• Provide an overview of normal menstruation and explain its absence during the initial months of lactation. (2006)
• Detail the changes observed in the ovary, uterus, vagina, and breast over the course of a menstrual cycle. (2003)
• Explain the effects of female sex hormones on the uterus during the menstrual cycle and discuss factors leading to cycle delay. (2002)
• Describe the changes occurring during the luteal phase of the menstrual cycle. (2018)